GameObject vs gameObject

Can anybody explain the difference between GameObject and gameObject and which one to use in a particular situation? Thanks.


Formal definition (from a reddit post):

to explain further, GameObject is the name of a class, which means a category, or type of object in Unity. You might use GameObject in a declaration of a variable or parameter type.

A gameObject, on the other hand, is a shortcut in a monobehaviour script, that is equivalent to the individual instance of GameObject that this script is currently attached to.

For example, you might have a variable declaration in a monobehaviour that goes:

GameObject someVariableName = gameObject;

The “GameObject”, part of this line, simply defines “someVariableName” as only accepting values of type GameObject . Attempting to state:

GameObject someVariableName = "foo";

would cause a compilation error because “foo” is a string, not a GameObject. So GameObject just tells Unity that you are excluding whatever it is you are doing to things that are part of the GameObject class. All other types will be rejected.

The part that states " = gameObject" is telling Unity to grab the reference to the current instance of GameObject that your script happens to be attached to, and to store it in someVariableName. If you try to use gameObject in this way in a script that is not a MonoBehaviour, it may also cause an error, since gameObject is a property built in to MonoBehaviour specifically, and not necessarily useable in other types of C# scripts in Unity.

There are some similar patterns in Unity with respect to other classes. For example, Transform refers to the general class of Transform objects , whereas “transform”, in a monobehaviour script, refers the current instance of Transform that is associated with the gameobject that your script happens to be attached to. So both Transform and GameObject are generally available classes in Unity, whereas gameObject and transform are handy properties of Monobehaviour scripts that refer to specific, individual instances of each class, which are connected to an individual instance of a script.

Actual usage is so varied as to be hard to nail down. My earlier example is not, as a real use case, all that useful, since you could just use “gameobject” instead of “someVariableName” anywhere in your script (I was trying to keep it simple). In general, though, think of GameObject as the title of a broad category objects, whereas gameObject is the specific, individual GameObject that your script is attached to.

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Thanks a lot for taking the time to write a comprehensive explanation. Transform vs transform looks like a good similarity as well.

You are welcome!

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